Heavy metals such as lead, zinc, mercury, silver, arsenic and the like can be present in trace amounts in all types of fuels such as crude oils. The amount can range from below the analytical detection limit (0.5 μg/kg) to several thousand ppb depending on the feed source. It is desirable to remove the trace elements of these metals from crude oils.
Various methods for removing trace metal contaminants in liquid hydrocarbon feed prior to fractional distillation have been developed. U.S. Pat. No. 6,350,372 B1 discloses utilizing a solubilized sulfur compound in combination with an absorbent carrier. U.S. Pat. No. 4,474,896 claims the use of absorbent compositions, mainly polysulfide based, for removal of elemental mercury from gaseous and liquid hydrocarbon streams. The use of absorbent includes a number of less than desirable attributes. Absorbent beds tend to get clogged by solid particulates in the crude, thus impeding the flow of the feed. Absorbents can also be very costly due to the large quantity needed. In U.S. Pat. No. 4,915,818, removal of mercury from liquid hydrocarbon condensate is disclosed. In this method, the liquid hydrocarbons are treated with a dilute aqueous solution of alkali metal sulfide salt.
There is still a need for improved methods for trace elements extraction from hydrocarbons.